There are two types of stains on teeth: extrinsic and intrinsic. Extrinsic stains are on the surface of the teeth, while intrinsic stains are between the tooth enamel and the dentin (the layer underneath the enamel). To remove these stains more effectively, we use Opalescence gel at our practice. Opalescence gels contain an active whitening ingredient that penetrates deep into the tooth enamel to remove discoloured molecules.